Metamorphic Rocks by YlhCT5

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									Metamorphic Rocks
  “New Rock From Old”
Metamorphic Rocks DVD Clip
        Metamorphic Rocks
• Metamorphism – takes place when
  preexisting rock is subjected to
  temperature and pressures unlike those in
  which it formed.
        Metamorphic Rocks
• Degrees of metamorphism
  (Composition)
  – Low-grade – the common sedimentary rock
    shale becomes more compact metamorphic
    rock slate
  – High-grade – features such as bedding
    planes, fossils, and vesicles that may have
    existed are obliterated.
  Formation of Metamorphic Rocks
The diagram below shows how the type of rock that forms
  during metamorphism indicates the conditions under
  which the metamorphism occurred.
         Metamorphic Rocks
• Metamorphic Settings
  – Contact metamorphism – when magma
    comes in contact with existing rock, heat
    changes the structure and mineral
    composition.
  – Regional metamorphism – changes in
    temperature & pressure over a large area
    result in changes in the texture, structure or
    chemical composition of a rock.
         Metamorphic Textures
• Foliated Texture – the alignment of the minerals gives
  the rock a layered or banded appearance. (parallel
  alignment or perpendicular to the compression)
• Foliated Rocks
   – Slate – very-fine grained and composed of mica flakes.
     Excellent cleavage. (most useful for roof and floor tiles,
     chalkboards, and billiard tables)
   – Schists – coarse-grained rock that forms when large
     amounts of heat and pressure are exerted on slate.
   – Gneiss – banded metamorphic rocks that contain mostly
     elongated and granular minerals. (most common minerals
     are quartz & feldspar)
       Metamorphic Textures
• Non-foliated Texture – resembles a coarse-
  grained igneous rock. (marble & quartzite)
• Non-foliated Rocks
  – Marble – a coarse, crystalline rock whose parent rock
    is limestone.
     • Has a hardness of 3 on Mohs Hardness Scale, so it is a
       popular building stone and comes in a variety of colors.
  – Quartzite – a very hard metamorphic rock whose
    parent rock is quartz sandstone.

								
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